Initially it was thought their baby had been called Ivy Blue but good friend Gwyneth Paltrow confirmed it was first name Blue, second name Ivy.
The 30-year-old singer gave birth to her daughter by caesarean section at Lenox Hill hospital in New York last night, according to the website eonline.com which reports 'multiple sources' have confirmed the news.
Rihanna was one of the first to tweet her congratulations: "Welcome to the world princess Carter! Love Aunty Rih." But Beyoncé, who has nearly 2.5 million Twitter followers but has never tweeted herself, hasn't rewarded them with an update. Fellow Destiny's Child singer Kelly Rowland was, however, detailing what she ate for breakfast.
According to the New York Daily News, Beyoncé checked into the Upper East Side hospital under the name Ingrid Jackson. Beyoncé is said to have spent $1.3 million booking out the entire fourth floor.
Baby rumours reached fever pitch last week with reports that Beyoncé had given birth to a a daughter called Tiana May Carter. It came after reports suggested that staff at St Luke's Roosevelt Hospital - a private facility in New York - had been told to prepare for a VIP arrival.
But Beyoncé's sister Solange, 25, put paid to those rumours, telling fans that the singer had spent New Year's Eve at her house party in Brooklyn, tweeting: "Shout out to my sister for being THE cutest pregnant woman ever!"
The baby will be the first child for the Single Ladies pop star and her husband Jay-Z and the second grandchild for her parents Tina and Mathew Knowles. Beyonce's younger sister Solange has a seven-year-old son Daniel Smith JR. Their parents' divorce was finalised a few weeks after 31 years of marriage. So some happy news for the family.
Many congratulations Bey and J!
What do you think of the name Blue Ivy (if true)? Good mix of traditional and not?